55 research outputs found
Latency Analysis of Systems with Multiple Interfaces for Ultra-Reliable M2M Communication
One of the ways to satisfy the requirements of ultra-reliable low latency
communication for mission critical Machine-type Communications (MTC)
applications is to integrate multiple communication interfaces. In order to
estimate the performance in terms of latency and reliability of such an
integrated communication system, we propose an analysis framework that combines
traditional reliability models with technology-specific latency probability
distributions. In our proposed model we demonstrate how failure correlation
between technologies can be taken into account. We show for the considered
scenario with fiber and different cellular technologies how up to 5-nines
reliability can be achieved and how packet splitting can be used to reduce
latency substantially while keeping 4-nines reliability. The model has been
validated through simulation.Comment: Accepted for IEEE SPAWC'1
Ultra-Reliable Low Latency Communication (URLLC) using Interface Diversity
An important ingredient of the future 5G systems will be Ultra-Reliable
Low-Latency Communication (URLLC). A way to offer URLLC without intervention in
the baseband/PHY layer design is to use interface diversity and integrate
multiple communication interfaces, each interface based on a different
technology. In this work, we propose to use coding to seamlessly distribute
coded payload and redundancy data across multiple available communication
interfaces. We formulate an optimization problem to find the payload allocation
weights that maximize the reliability at specific target latency values. In
order to estimate the performance in terms of latency and reliability of such
an integrated communication system, we propose an analysis framework that
combines traditional reliability models with technology-specific latency
probability distributions. Our model is capable to account for failure
correlation among interfaces/technologies. By considering different scenarios,
we find that optimized strategies can in some cases significantly outperform
strategies based on -out-of- erasure codes, where the latter do not
account for the characteristics of the different interfaces. The model has been
validated through simulation and is supported by experimental results.Comment: Accepted for IEEE Transactions on Communication
Interference Spins: Scheduling of Multiple Interfering Two-Way Wireless Links
Two-way is a dominant mode of communication in wireless systems. Departing
from the tradition to optimize each transmission direction separately, recent
work has demonstrated that, for time-division duplex (TDD) systems, optimizing
the schedule of the two transmission directions depending on traffic load and
interference condition leads to performance gains. In this letter, a general
network of multiple interfering two-way links is studied under the assumption
of a balanced load in the two directions for each link. Using the notion of
interference spin, we introduce an algebraic framework for the optimization of
two-way scheduling, along with an efficient optimization algorithm that is
based on the pruning of a properly defined topology graph and dynamic
programming. Numerical results demonstrate multi-fold rate gains with respect
to baseline solutions, especially for worst-case (5%-ile) rates.Comment: Accepted for publication in IEEE Communications Letter
Location-Quality-aware Policy Optimisation for Relay Selection in Mobile Networks
Relaying can improve the coverage and performance of wireless access
networks. In presence of a localisation system at the mobile nodes, the use of
such location estimates for relay node selection can be advantageous as such
information can be collected by access points in linear effort with respect to
number of mobile nodes (while the number of links grows quadratically).
However, the localisation error and the chosen update rate of location
information in conjunction with the mobility model affect the performance of
such location-based relay schemes; these parameters also need to be taken into
account in the design of optimal policies. This paper develops a Markov model
that can capture the joint impact of localisation errors and inaccuracies of
location information due to forwarding delays and mobility; the Markov model is
used to develop algorithms to determine optimal location-based relay policies
that take the aforementioned factors into account. The model is subsequently
used to analyse the impact of deployment parameter choices on the performance
of location-based relaying in WLAN scenarios with free-space propagation
conditions and in an measurement-based indoor office scenario.Comment: Accepted for publication in ACM/Springer Wireless Network
A Tractable Model of the LTE Access Reservation Procedure for Machine-Type Communications
A canonical scenario in Machine-Type Communications (MTC) is the one
featuring a large number of devices, each of them with sporadic traffic. Hence,
the number of served devices in a single LTE cell is not determined by the
available aggregate rate, but rather by the limitations of the LTE access
reservation protocol. Specifically, the limited number of contention preambles
and the limited amount of uplink grants per random access response are crucial
to consider when dimensioning LTE networks for MTC. We propose a low-complexity
model of LTE's access reservation protocol that encompasses these two
limitations and allows us to evaluate the outage probability at click-speed.
The model is based chiefly on closed-form expressions, except for the part with
the feedback impact of retransmissions, which is determined by solving a fixed
point equation. Our model overcomes the incompleteness of the existing models
that are focusing solely on the preamble collisions. A comparison with the
simulated LTE access reservation procedure that follows the 3GPP
specifications, confirms that our model provides an accurate estimation of the
system outage event and the number of supported MTC devices.Comment: Submitted, Revised, to be presented in IEEE Globecom 2015; v3: fixed
error in eq. (4
What Can Wireless Cellular Technologies Do about the Upcoming Smart Metering Traffic?
The introduction of smart electricity meters with cellular radio interface
puts an additional load on the wireless cellular networks. Currently, these
meters are designed for low duty cycle billing and occasional system check,
which generates a low-rate sporadic traffic. As the number of distributed
energy resources increases, the household power will become more variable and
thus unpredictable from the viewpoint of the Distribution System Operator
(DSO). It is therefore expected, in the near future, to have an increased
number of Wide Area Measurement System (WAMS) devices with Phasor Measurement
Unit (PMU)-like capabilities in the distribution grid, thus allowing the
utilities to monitor the low voltage grid quality while providing information
required for tighter grid control. From a communication standpoint, the traffic
profile will change drastically towards higher data volumes and higher rates
per device. In this paper, we characterize the current traffic generated by
smart electricity meters and supplement it with the potential traffic
requirements brought by introducing enhanced Smart Meters, i.e., meters with
PMU-like capabilities. Our study shows how GSM/GPRS and LTE cellular system
performance behaves with the current and next generation smart meters traffic,
where it is clearly seen that the PMU data will seriously challenge these
wireless systems. We conclude by highlighting the possible solutions for
upgrading the cellular standards, in order to cope with the upcoming smart
metering traffic.Comment: Submitted; change: corrected location of eSM box in Fig. 1; May 22,
2015: Major revision after review; v4: revised, accepted for publicatio
Sustainable Wireless Services with UAV Swarms Tailored to Renewable Energy Sources
Unmanned Aerial Vehicle (UAV) swarms are often required in off-grid
scenarios, such as disaster-struck, war-torn or rural areas, where the UAVs
have no access to the power grid and instead rely on renewable energy.
Considering a main battery fed from two renewable sources, wind and solar, we
scale such a system based on the financial budget, environmental
characteristics, and seasonal variations. Interestingly, the source of energy
is correlated with the energy expenditure of the UAVs, since strong winds cause
UAV hovering to become increasingly energy-hungry. The aim is to maximize the
cost efficiency of coverage at a particular location, which is a combinatorial
optimization problem for dimensioning of the multivariate energy generation
system under non-convex criteria. We have devised a customized algorithm by
lowering the processing complexity and reducing the solution space through
sampling. Evaluation is done with condensed real-world data on wind, solar
energy, and traffic load per unit area, driven by vendor-provided prices. The
implementation was tested in four locations, with varying wind or solar
intensity. The best results were achieved in locations with mild wind presence
and strong solar irradiation, while locations with strong winds and low solar
intensity require higher Capital Expenditure (CAPEX) allocation.Comment: To be published in Transactions on Smart Gri
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